Ignition circuit



lNov. 28, 1950 R. .1. MlLLER IGNITION CIRCUIT Original Filed June 21,1943 2 Sheets-Sheet l 272 7: Z 337mm Qaymond d. Mf//er ...IIISIIIIIIIIw, a/M- Nov. 28, 1950 R. J. MILLER IGNITION CIRCUIT 2 Sheets-Sheet 2Original Filed June 2l, 1943 443 445/ Roqmonc/ J Mil/er @ttor/M m W Mm nf r i 3 /l ww....n....wuwwwwmmwwwwmmw. xS V... .........n..l1. A .V 4 1-s e Patented Nov. 28, 1950 UNITED STATES PATENT oEFlcE IGNITIN CIRCUITRaymond J. Miller, Detroit, Mich.

'Original application June 21, 1943, Serial No.

491,584. Divided and this application September 23, 1948, Serial No.50,720

8 Claims. 1

This invention relates to engines, and more particularly to improvedignition systems for engines.

In conventional ignition systems, the voltage is stepped up and istransmitted through single high tension leads to the spark plugs to firethe combustible charge in the cylinders of the engine. Single electrodespark plugs are employed, and the circuit is completed by enclosing theentire ignition system in metallic covers, or by utilizing the engine asa ground to complete the circuit. The entire engine and vehicle thusbecomes a part of the ignition circuit and acts as a variable capacitor.

' In accordance with conventional practice, a single high tension coilis used for each engine. In multi-cylinder engines, this coil isfrequently overtaXed because the reluctance will not permit the coil tocompletely collapse before the next impluse is imposed on-it to providethe necessary high voltage sparkto fire the neXt cylinder when theengine is operating at high speed. In certain high speed engines it hasbeen necessary to employ two or more high tension coils per engine toprevent overtaxing the coils.

Considerable current from the high tension coils is lost before reachingthe spark plugs through leakage from the high. tension wires connectedto the spark plugs. The efficiency of ignition systems now in use istherefore considerably below that desired.

In ignition systems as presently employed, undesirable signals areemitted whenever the engine is running. These undesirable signals areemitted from:

1. The sparking of high tension current jumping from the rotatingdistributor arm to the successive distribution points.

2. The sparking at the spark plug electrodes.

In military vehicles, the enemy can establish listening stations andreadily pick up these undesirable signals emitted from the ignitionsystem. The exact location of a vehicle or a convoy of vehicles can thusreadily be ascertained by triangulation from spaced listening stations.Accurate gun re can then be brought to bear cn the vehicle or convoy ofvehicles.

These undesirable signals emanating from the ignition system interferewith radio communication, both sending and receiving, and causedistortion of the images in the operation of television sending andreceiving apparatus.

' Efforts have been made to overcome these objectionable features byusing Suppressors hooked within the circuits; by the use of shieldingsurrounding the wires and electrical units, and by bonding the componentparts of the vehicle together to maintain good electrical contactsbetween all parts of the vehicle. These efforts have not been verysuccessful because of the expense and time required in theirinstallation and the diiliculty of maintaining them in proper workingcondition.

An object of this invention is to provide a closed circuit ignitionsystem wherein the above enumerated disadvantages are eliminated.

A further object of the invention resides in the provision of animproved ignition system wherein low voltage current is transmitted by adistributor to a compact transformer associated with each spark plug ofthe engine.

Another object is to provide an ignition system for an engine whereindual electrode spark plugs insulated from the engine are supplied byhigh voltage circuits, each of which is completely contained within itsassociated spark plug.

Yet another object resides in the provision of a closed circuit ignitionsystem wherein lowY voltage current is induced and is transmittedthrough low tension wires to small transformers positioned on dualelectrode spark plugs insulated from the engine.

A further object is to provide an ignition system wherein transformershaving primary and secondary windings wound in a bell shaped mannerextend down over the body portions of dual electrode spark plugs toproduce directed magnetic fields to provide controlled electric sparksat the electrodes of the plugs, and produce a blow-out condition at thespark gap to provide sharper more controlled points of ignition.

Another object of the invention resides in the provision of an ignitionsystem wherein it is unnecessary to employ continuous shielding, bondingor Suppressors to prevent the transmission of undesirable signalscapable of indicating the location of the vehicle and interfering withradio or television transmission or reception.

Other objects and advantages of this invention will be apparent from thefollowing detailed description considered in connection with theaccompanying drawings7 submitted for purposesl of illustration only andnot intended to define the scope of the invention, reference being hadfor that purpose to the subjoined claims.

In the drawings wherein similar reference characters refer to similarparts throughout the several views:

' Fig. 1 is an enlarged sectional view illustrating a dual electrodespark plug having a transformer associated therewith.

Fig. 2 is a bottom plan view of the spark plug 3 illustrated in Fig. l,taken substantially on the line 2-2 of Fig. 1 looking in the directionof the arrows.

Fig. 3 is a longitudinal sectional view of a modied form of dualelectrode spark plug.

Fig. 4 is a longitudinal sectional View illustrating another modifiedform of dual electrode spark plug.

Fig. 5 is a fragmentary sectional view illustrating a casing adapted tosurround a portion of a dual electrode spark plug, to Protect it againstthe entrance of moisture.

Fig. 6 is a fragmentary sectional View illustrating an adjustableresistor member adapted to be interposed between an electrode of thespark plug and a source of electric current.

Fig. '7 is a view similar to Fig. 6 illustrating a modified form ofresistor member.

Fig. 8 is a longitudinal sectional View illustratinga further modifiedform of dual electrode spark plug.

Fig. 9 is a sectional View taken substantially on the line 0 0 of Fig.8, looking in the direction' of the arrows.

Before explaining in detail the present invention it is to be understoodthat the invention is not limited in its application to the details ofconstruction and arrangement of parts illustrated in the accompanyingdrawings, since the invention is capable of other embodiments and ofbeing practiced or carried out in various ways. Also it is to beunderstood that the phraseology or terminology employed herein is forthe purpose of description and not of limitation.

One desirable form of dual electrode spark plug having the primary andsecondary coils mounted thereon is illustrated in detail in Figs. 1 and2. The spark plug 40 comprises a base member |00 having threads |02whereby the plug may be secured in the combustion chamber of an engine,and a wrench receiving portion |04 preferably of hexagonal shape.

The inner electrode 54 preferably has a body portion |06 and is providedadjacent its bottom end with an enlarged outwardly flaring portion |08.The outer electrode 56 is concentrically mounted on the inner electrode54 and is insulated therefrom by suitable insulators ||0, ||2 and H4.,and is insulated from the base member |60 by means of a suitableinsulator IIS.

The insulator ||0 preferably extends over the entire cylindrical bodyportion |66 of the inner electrode 54, and may be formed of any suitablematerial such for example as mica. The insulators I|2 and I4 may beconcentrically mounted on the insulator ||G and may for example beformed of ceramic material.

It will be noted that the lower body portion of the outer electrode 56is ared outwardly in the base member |00. The insulator H6 may forexample be formed of mica and may be tapered in accordance with thetaper of the lower body portion of the outer electrode 56 whereby theunit consisting of the inner and outer electrodes 54 and 55 with theinsulators I I0, ||2, ||4 and ||6 may be securely bonded to the basemember |00 by means of upper and lower flanges |8 and |20 positioned tooverlie the insulator i I6.

Discs |22 and |24 formed of copper or other suitable material may beinterposed between the insulator H2 and the lower surface of an inwardlydirected ange |25 formed on the outer electrode 56, and the insulator |4and the upper surface of the flange |25 to take up mechanicaldifferential in the manufacture of the parts,

CII

The upper end of the outer electrode is provided with threads to receivethe base of a coil supporting member |3| surrounding the plug. Themember |3| is formed adjacent its upper end with a section of reduceddiameter to receive an insulator |33 formed of any suitable materialsuch as Bakelite.

Wrapped about the insulator |33 and the lower portion of the member I3|is the primary coil 36 wound with relatively coarse wire |36 as iscustomary. Surrounding the primary coil 36 is a core |33 formed of ironor steel or other suitable electrical conducting material.

The secondary coil 52 preferably formed of smaller wire |40 than thewire |36 of he primary coil 36 is wrapped about the core |38. Theprimary and secondary coils 36 and 52 are covered at the top by means ofan insulator |42 formed of Bakelite or other suitable material having asection |44 of reduced diameter to lit within the core |38. A casing |48is provided to overlie the insulator |42 and secondary coil 52 tofunction as an additional core to assist the core |38. The casing |46 issuitably secured to an upwardly directed flange |54 carried by the coilsupporting member |32.

A furl |50 is positioned on the insulator |42 and connected through awire |52 extending through the insulator |42 to the other end of theprimary coil 36. The furl |50 may be separated from the pole |53 bymeans of a suitable portion |54 of the insulator |42, and from thecasing |46 by means of a suitable insulator portion |56.

The core member |38 interposed between the primary and secondary coils36 and 52 respectively, being of bell shaped contour, and the casing |46surrounding the secondary coil 52 concentrate the magnetic lines offorce. This concentrated electrical field induces a strong inductioncurrent in the secondary coil 52.

Opposite ends of the secondary coil 52 are connected to the inner andouter electrodes 54 and 56 of the spark plug 40. One end of the coil 52may be connected. through a wire |58 embedded in the insulator |42 to aresistor' |60 engaging the end of the cylindrical body portion |06 ofthe central electrode 54.

The resistor |60 may be guided in a portion |62 of reduced diameter ofthe insulator |33, and may be yieldingly urged into engagement with thebody portion |06 of the central electrode 54 by means of a springportion |64 of the wire |58. The resistor |60 may be made of carbon orother good resisting material. Where a resistor similar to thatillustrated is employed, the electrodes 54 and. 56 of the plug 40 willnot be subjected to such prolonged current and will therefore be longerlived because the resistors tend to smooth out the electrical surge.

The other end of the secondary coil 52 is connected to the coil carryingmember |3| as illustrated at |66. The flow of current is preferably fromthe secondary coil 52 through the central electrode 54, thence acrossthe spark gap |68 to the outer electrode 56 and back to the secondarycoil 52.

The inner and outer electrodes 54 and 56 and the coil supporting member|3| may be formed of any suitable material having good electricalconducting characteristics, such for example as steel.

It will be noted that this spark plug is thoroughly shielded againstmoisture and is advantageously insulated to prevent undesired elec- *fil1.95565 Q1" ShQrt rcutnz. Greater voltage can therefore be exerted tofire the charge in the cylinder of the engine.

The entire circuit is self-contained and it is not necessary to use theengine or any other part of the vehicle as a ground. Since the vehicleis not used as a ground for the ignition circuit it is not effective asa variable capacitor, and the necessity for bonding the component partsof the vehicle together is entirely eliminated.

In view of the fact that low voltage current is transmitted to thetransformers associated with the spark plugs, it is unnecessary toemploy shielding on the spark plug wires to prevent leakage from thehigh tension wires as is now customary.

No spark gap is present in the distributor as the low intensity currentis induced in the induction coils by movement of the magnet withreference to the coils. Undesirable signals from this source aretherefore eliminated. The spark gap between the electrodes of the sparkin the combustion chambers being insulated from the engine will nottransmit undesirable signals as is customary with presently usedignition systems.

Fig. 3 illustrates a somewhat modified form of spark plug over thatdisclosed in Figs. 1 and 2. Corresponding parts have therefore beengiven corresponding reference numerals with the addition of 100.

It will be noted that the inner electrode 206 is shorter than the innerelectrode of the plug illustrated in Figs. 1 and 2, and that the outerelectrode 226 is provided with a plurality of spaced heat radiating fins210, positioned beneath the threaded portion 230.

The lower portions of the inner and outer electrodes 206 and 226 haveparallel, preferably angularly disposed side walls 212 and 214respectively to define there-between a spark gap 216. The parallel sparkgap 216 gives greater opportunity for the plug to clear itself in theevent of fowling and will therefore frequently prevent short circuitingof the plug.

A transformer of the general type illustrated in Fig. l may be employedwith the plug illustrated in Fig. 3, or it may be connected toconventional magneto or distributor circuits. When so used, the centralelectrode 206 is preferably connected to the high tension lead, and theouter electrode 226 is grounded back to the electrical source. Aconfined circuit is thus provided in conventional magneto or distributorcircuits whereupon it is unnecessary to employ the body of the engine orvehicle to complete the circuit from the source of electric current suchas a battery or magneto.

The spark plug illustrated in Fig. 4 is similar in many respects to thatillustrated in Fig. 1. Corresponding parts have therefore been givencorresponding reference numerals with the addition of 200.

It will be noted that the base member 300 is provided adjacent its upperend with screw threads 380 to receive a threaded plug 382 having aninwardly directed flange 384 to overlie the upper edge of the insulator3|6 to clamp the component parts of the spark plug in assembledrelation. The inner electrode 306 is provided adjacent its upper endwith a threaded portion 386 to receive a threaded member 388 to engagethe insulator 3| 4 and maintain the upper portions 0f the plug in theassembled relation. This plug may be readily disassembled for cleaningpurposes or for the replacement of new elements.

The wire 315 may be connected through the resistor or contactor 36| withthe central electrode 306, and the wire 311 may be connected to theouter electrode 326 as illustrated. I'he housing 38| is provided with athreaded ring 390 to which the wire 311 may be connected. The ring 390may be screwed onto the threaded portion 330 of the outer electrode 326to securely seal the upper end of the spark plug assembly.

If desired a shield may be positioned on the spark plug where the dualelectrode plugs are employed without the transformers, and the highvoltage current is transmitted to one of the electrodes of the sparkplug. Fig. 5 illustrates one desirable form of shield 40| having athreaded end section 403 adapted to receive a furl 405 surrounding thecasing 319 having the current carrying wires 315 and 311 housed therein.If desired the casing 40| may be split and have overlapping edges tosecurely seal the upper end of the spark plug against the entrance ofmoisture. The shield may be formed at the bottom end with an inwardlydirected flange 401 to overlie the housing V38| of the embodimentillustrated in Fig. 19.

Fig. 6 illustrates a modified form of resistor element adapted to beinterposed between one of the yelectrodes of the spark plug and the wire4| connected to a transformer associated with the spark plug or to ahigh tension wire, where separate transformers are not employed at thespark plugs. A removable and replaceable resistor element 4|3 may beinterposed between the electrode and a shell 4|5, connected to the wire4| I, and shaped to receive the resistor 4| 3. A spring 4|1 yieldinglyurges the resistor 4|3 into engagement with the electrode 406 of theSpark plug. The resistor 4| 3 may be removed and replaced by resistorsof different lengths to vary the resistance, or resistors formed ofdifferent material but of the same length may be employed to vary theresistance introduced. The resistor 4|3 may advantageously be formed ofcarbon, powdered metal, tungsten or other suitable material.

Fig. 7 illustrates a further modified form of resistor wherein aresistor element 42| having a groove 423 formed adjacent one end isprovided with a spring clip 42 5. The spring clip 425 may be introducedinto a cylinder 421 formed in a threaded member 43| operably connectedto one of the electrodes 406 of the spark plug. Resistors of this typemay be formed of different material to provide the desired variation ofresistance, and may also be formed of different lengths to provide thedesired operating characteristics.

Figs. 8 and 9 illustrate a further modified form of spark plug havingspaced parallel electrodes 435 and 431. The electrodes are positioned ina threaded base member 439 adapted to be secured in the cylinder of anengine to position the spark gap forming portions 44| and 443 of theelectrodes 435 and 431 respectively in the combustion chambers of theengine.

The electrodes 435 and 431 may be insulated from each other and from thebase member 439 and engine by any suitable form of insulating materialsuch for example as stacked mica disks 445. It will be apparent that thelowermost disk is supported on shoulders 441 formed in the base member449 and in the lower shanks of the electrodes 435 and 431. The upper endof the base member 439 is formed with an inwardly directed flange 449 tooverlie disks of larger diameter and maintain the plug in the assembledrelation.

It will be noted that the electrode 435 is somewhat longer than theelectrode 431 to separate their upper ends and prevent short circuitingbetween the upper ends of the electrodes and to insure the formation ofthe charge firing spark in the spark gap between the portions 44| and443 of the electrodes.

A ring 453 is positioned adjacent the top of the electrode 43'! and iscontoured to overlie a. group of the disks 445 and maintain a desiredpressure on the disks 445 between it and the flange 449 of the basemember 439. The upper end of the electrode 431 is flared outwardly asillustrated at 455 over the ring 453 to insure good electrical contacttherewith. The inner portion of the ring 453 may be cut out, andcontoured mica or other suitable insulating disks 459 positioned thereinas illustrated in Fig. 8.

A ring 135i may be positioned above the smaller disks surrounding thelonger electrode 435, and the upper end of the electrode 435 may be aredoutwardly as illustrated at 451 to maintain a desired pressure on theupper disks and thus insure good electrical contact therewith.

A transformer 463 similar to that illustrated in Fig. 1 may be employedwith this spark plug, the low intensity contacts from the source ofelectrical energy being connected with opposite ends of the primaryWinding. One end of the secondary winding of the transformer may beconnected to the electrode 435 through a contactor 467 engaging the ring46| engaging the electrode 435. The other end of the secondary windingof the transformer' may be connected to the electrode 43'! through thering 453, threaded to receive the transformer 4553 as illustrated at455.

It will be understood that if desired this spark plug may be usedwithout the transformer as discussed above.

This application is a division of my application Serial Number 491,584,led June 21, 1943, now Patent 2,461,293 issued February 8, 1949.

I claim:

l. In a spark producing assembly, a central spindle terminating in asparking electrode, a transformer having its primary winding surroundingsaid spindle, and its secondary winding surrounding said primarywinding, a metallic casing surrounding said secondary winding, saidcasing having an extension surrounding said sparking electrode andconstituting a co-operating electrode, and means connecting the ends ofsaid secondary winding with said spindle and casing, respectively.

2. In a spark producing assembly, a central spindle terminating in asparking electrode, a transformer having its primary winding surroundingsaid spindle, and its secondary winding surrounding said primarywinding, a metallic casing surrounding said secondary winding, saidcasing having an extension surrounding said sparking electrode andconstituting a cooperating electrode, means connecting the ends of saidsecondary winding with said spindle and casing, respectively, a pair ofconcentric terminal posts at the outer end of the assembly, and meansconnecting the ends of said primary winding to said posts.

3. In a spark producing assembly, a central spindle terminating in asparking electrode, a transformer having its primary winding surroundingsaid spindle, and its secondary winding surrounding said primarywinding, a metallic casing surrounding said secondary winding, saidcasing having an extension surrounding said 5 sparking electrode andconstituting a co-operating electrode, means connecting the ends of saidsecondary winding with said spindle and casing, respectively, anattaching base for said assembly, and means for insulating said secondelectrode from said attaching base.

4. In a spark producing assembly, a central spindle terminating in asparking electrode, a transformer having its primary winding surroundingsaid spindle and its secondary winding surrounding said primary winding,a second electrode surrounding said first-named electrode, and meansconnecting the ends of said secondary Winding with said spindle andsecond electrode, respectively.

5. In a spark producing assembly, a central spindle terminating in asparking electrode, a transformer having its primary winding surroundingsaid spindle and its secondary winding surrounding said primary winding,a metallic casing surrounding said secondary winding, said casing havingan extension surrounding said sparking electrode and constituting acooperating electrode, means connecting the ends of said secondarywinding with said spindle and casing, respectively, a pair of concentricterminal posts at the outer end of the assembly, and means connectingthe ends of said primary winding to said posts.

6. In a spark producing assembly, a central spindle terminating in asparking electrode, a transformer having its primary winding surroundingsaid spindle and its secondary winding surrounding said primary winding,a metallic casing surrounding said secondary winding, said casing havingan extension surrounding said sparking electrode and constituting aco-operating electrode, means connecting the ends of said secondarywinding with said spindle and casing, respectively, an attaching basefor said assembly, and means for insulating said second electrode fromsaid attaching base.

'7. In an ignition system for an internal combustion engine, thecombination of a dual electrode spark plug and a transformer havingprimary and secondary windings comprising a central electrode, a secondelectrode concentrically mounted relative to the central electrode andcooperating therewith to form a spark gap, a base having externalthreads adapted to be received in the cylinder of the engine, insulatingmeans between the central and second electrode and between the base andthe second electrode, the primary winding concentrically mounted on saidelectrodes, spaced ttings operably connected to the opposite ends of theprimary winding, the secondary winding being concentrically disposedrelative to the primary winding, connecting means between one end of thesecondary winding and the central electrode, and connecting meansbetween the opposite end of the secondary vlinding and said secondelectrode.

8. In an ignition system, the combination of a dual electrode spark plugand a transformer having primary and secondary windings comprising acentral longitudinally extending electrode, a second electrodeconcentrically mounted relative to the central electrode and cooperatingtherewith to form a spark gap, insulating means between the central andsecond electrode, a base having external threads adapted to be receivedin the cylinder of an engine, insulating means between said base and thesecond electrode, a transformer supporting flange threaded to the secondelectrode, a bell shaped primary winding supported by said flange andconcentrically mounted on the electrodes, spaced fittings operablyconnected t to opposite ends of the primary Winding, a. secondary bellshaped winding being supported by said flange and concentricallydisposed relative to the primary winding, connecting means between oneend of the secondary winding and the central electrode and connectingmeans between the opposite end of the secondary winding and said secondelectrode.

RAYMOND J. MILLER.

REFERENCES CITED The following references are of record in the file ofthis patent:

Number 10 UNITED STATES PATENTS Name Date Orswell Dec. 14. 1915 PowellOct. 21, 1919 Sullivan Dec. 18, 1923 Hooven Nov. 21, 1939 Robinson Dec.16, 1941 Harkness et al. Jan. 21, 1947

